In recent years, advances in micromachining technology have lead to the industrial production of microparts having minute shapes on the order of micrometers. These microparts have a size ranging from several millimeters to as small as several hundreds of micrometers in, for example, electronic devices, such as digital cameras, mobile telephones, etc. Therefore, dies for manufacturing the microparts require the geometric precision on the order of sub-micrometers to nanometers. The present inventors have proposed a technique of measuring and evaluating minute shapes of microparts in a previous patent application entitled “MEASURING DEVICE AND METHOD USING PARTICLE PROBE TRAPPED BY RADIATION PRESSURE” (see Patent Document 1).
The technique described in Patent Document 1 is performed as follows. A particle having a diameter of 8 μm is irradiated with laser light and trapped by the radiation pressure of the light. The trapped particle is caused to approach an object to be measured (also referred to as a target object) while the intensity of the laser light is modulated. The vibration of the particle in this case is monitored. A change occurs in the vibration when the particle contacts the target object. Based on the change, a position of the target object is calculated. By using this technique, the present inventors have successfully measured the shape of the target object on the order of several tens of nanometers.